1. Field of the Invention
The present invention relates to a novel antioxidant and a novel oxidation resistant polyunsaturated oil comprising the antioxidant. More particularly, the present invention relates to a novel antioxidant which is safe for human health, excellent in the antioxidation effect and particularly suitable for preventing oxidation of unsaturated fatty acids, esters of unsaturated fatty acids and various products comprising these acids and esters. The present invention also relates to a novel oxidation resistant polyunsaturated oil which is made by giving strong antioxidation activity to eicosapentaenoic acid, docosahexaenoic acid, esters of these acids or fats comprising eicosapentaenoic acid or docosahexaenoic acid as the fatty acid component by addition of an antioxidant comprising musizin as the effective component.
2. Description of the Prior Art
Antioxidants are generally utilized for oil, fats and products containing oil and fats for the purpose of preventing change of smell, taste and color by rancidity. Examples of such generally utilized antioxidants are synthetic antioxidants, such as butylhydroxyanisole (BHA) and butylhydroxytoluene (BHT), and natural antioxidants, such as tocopherol, L-ascorbic acid, citric acid, melanoidin, flavonoids, amino acids, phitic acid and gallic acid.
However, the synthetic antioxidants such as BHA and BHT are not always safe for human health even though they are less expensive and excellent in the antioxidation effect and application of them to foods are being considered to have problems. On the other hand, the natural antioxidants do not have sufficient antioxidation effect even though they are safe for human health. Thus, the generally utilized antioxidants have a disadvantage while they have an advantage. Development of novel antioxidants having the excellent antioxidation effect and the safety for human health simultaneously has been strongly desired.
Recently, polyunsaturated fatty acids, such as eicosapentaenoic acid and docosahexaenoic acid, are attracting attention because of their useful physiological effect, such as suppression of coagulation of blood platelet, depression of neutral fats in blood, depression of cholesterol in blood, depression of viscosity of blood, antitumor activity and the like, and being utilized for functional foods, food additives, medicines, toiletries, feed stuffs and like others.
However, the polyunsaturated fatty acids of this kind are usually contained in fish oils. Because they are oxidized very rapidly and the mechanism of the oxidation is different from oxidation of fats and oils of land animals and plants, the oxidation can not be effectively prevented by the generally utilized antioxidants described above.
Musizin which is a naphthalenic compound has been known to have antioxidation effect (Laid Open Japanese Patent Publication Showa 61-66787). However, synergistic effect of musizin with other antioxidants has not been known and no example of utilization of synergistic effect of musizin and tocopherol has been published.
Antioxidation activity of musizin against polyunsaturated fatty acids and polyunsaturated oils and fats containing polyunsaturated fatty acids as the fatty acid components has not been known at all and no example of utilization of musizin for polyunsaturated fatty acids and polyunsaturated oils and fats has been published.